(svn r12776) -Fix: [OSX] In some rare cases when using an uncalibrated monitor the system colour space could not be retrieved. Show an error when this happens instead of just trying an assertion.

src/video/cocoa/wnd_quartz.mm

@@ -175,7 +175,8 @@ static CGColorSpaceRef QZ_GetCorrectColorSpace()
 			CMCloseProfile(sysProfile);
 		}
 
-		assert(colorSpace != NULL);
+		if (colorSpace == NULL)
+			error("Could not get system colour space. You might need to recalibrate your monitor.");
 	}
 
 	return colorSpace;